The elderly account for 1/3rd of prescription drug consumption in the United States and are at greater risk for medication errors (MEs) and adverse drug events (ADEs). They are also more likely to have low health literacy that increases the possibility of medication-related problems. Data on MEs and ADEs are collected predominantly in hospitals where it is easier to monitor such errors and to identify patients experiencing medication-related problems. This approach is not optimal in the United States, because here most medications are prescribed in the outpatient setting by primary care physicians. The proposed study will describe the spectrum of MEs and ADEs in the elderly and how health literacy affects medication safety. The aim of this application is to determine the frequency, type, severity, and preventability of MEs among elderly primary care patients who have low (inadequate and marginal) functional health literacy (FHL) vs. elderly primary care patients who have adequate FHL. Furthermore, we will conduct cognitive interviews to understand why MEs may have occurred. The study will be conducted in a primary care research network, the Southern Primary care Urban Research Network (SPUR-NetSM), which is located in Houston, Texas. In this application, we propose to evaluate medications used by 300 elderly patients from diverse ethnic and socioeconomic backgrounds who are seen by primary care providers in outpatient clinics. This is a unique study, because our main outcome measure is ME as it occurs in primary care clinics;. Moreover, we will generate findings and compare types and rates of MEs and ADEs among elderly patients who have different ethnicity, socioeconomic status, and literacy. Findings from this study will be used to design interventions for medication-safety-promotion education programs to be implemented and evaluated within primary care clinics. The proposed research is innovative, because it will provide an understanding of MEs and ADEs in a diverse primary care population and the association of health literacy with such errors. The outcomes of the proposed research will be significant, because millions of the American elderly will receive improved quality of care. [unreadable] [unreadable]